Vulcanization of halogenated rubbery polymers



United States Patent The present invention relates to improved vul-canizable compositions of halogenated rubbery polymers. More particularly, it deals with curing halogenated isooletlnmultiolefin copolymers, e.g., halogenated butyl rubber, at an accelerated rate to give a vulcanizate of improved physical and dynamic properties.

This application is a continuation of application Serial No. 67,886, filed November 8, 1960, now abandoned.

Copolymers of the above general class, particularly Where the copolymers contain about 85 to 99.5 Wt. percent of a C to C isoolcfin, e.g., isobutylene, 3-methyl butene-l, with about to 0.5 Wt. percent of a multi- -olelin of about 4 to 14 carbon atoms, e.g., myrcene, isoprene, butadiene, etc., are Well known in the literature as butyl rubber. For example, see Synthetic Rubber, by G. S. Whitby (i954), and US. Patent 2,356,l28 among many others. Halogenated butyl rubber-type copolymers are produced by halogenating butyl rubber in a manner which does not substantially degrade its molecule Weight but, however, gives a rubbery product of substantially ditferent properties than the unhalogenated material. Butyl rubber may be halogenated at temperatures of to 200 (3., preferably 0 to 100 C., at pressures of 0.5 to 900 p.s.i.a. With suitable halogen ating agent such as gaseous chlorine, liquid bromine, iodine monochloride, etc. Halogenation may be accomplished in various Ways. For example, the halogenation agent, e.g., chlorine, may be added to a solution of the copolymcr in a suitable inert liquid organic solvent. The resulting halogenated polymer may be recovered by precipitation with a nonsolvent at about 0 to 180 spray drying, or by flashing off the hydrocarbon solvent by injection into a hot water bath.

Preferably, the degree of halogenation is carefully regulated so that the halogenated copolymer contains at least 0.5 Wt. percent of combined halogen, but not more than about one atom of combined fluorine or chlorine per double bond in the polymer, nor more than three atoms of combined bromine or iodine per double bond. A more detailed description of the formation of chlorinated butyl rubber may be had by referring to coassigned US. Patent 2,944,578, filed May 31, 1955.

The halogenated copolymer has a viscosity range average molecular Weight of about 100,000 to 2,000,000, and a mole percent unsaturation of between 0.1 to 20, preferably lcss than 10. As hereinafter employed in the specification, the term halogenated butyl rubber denotes the above described halogenated copolymers of a major portion of a C to C isoolefin and a minor portion of a C to C multioletin.

Various cure systems have been suggested for curing halogenated butyl rubber polymers. Examples of systems which have been investigated are the following: 2,4-dithiobiuret, 4-amino-antipyrine, tr-iphenyl guanidine, indole, Z-thiobarbituric acid, 1,2-diphenoxyethane, 4,4- bis(O methoxyphenyl) carbonate, 4,4 bis(dimethylamino) thiobenzophenone, bis(rnercaptoalkyl) sulfide, zinc acrylate, quinone imine compounds, ethylene ditbiocyanate, ethylene monoand dithiocarbonate, dicarboxylic acids, thiobenzoic acids, N-(Z-thiazolyl) thiourea,

3,196,135 Patented July 20, 1965 alkyl, aryl or alkyl-aryl tin oxides, 2,2'dithiodibenzoic acid, paraformaldehyde and/or nonyl phenol, 2-thiazol-idinethionc, thiazoles and derivatives of thiazoles such as amino thiazole, p-aminophenyl-mercaptoacetic acid, condensation products of polymerized linoleic acid with polyamines, imidazoles such as Z-aminobenzimidazole, 2mercaptoimidazoline (particularly in the presence of anhydrous silica of pH 3.5 to 4.5), polymeric bottoms remaining recovered from the production of aldehydephenol reaction products, polymeric aniline-acetone reaction products (Age Rite Resin D), pentaerythritol tetrathioglycolate, dithiooxamides, etc. Particularly for covulcanizing halogenated butyl with high unsaturation rubbers, cure systems such as the combination of triphenyl guanidine, sulfur and zinc oxide, or the combination of tetramethyl thiuram disulfide and Zinc oxide have been employed.

However, due to the relatively saturated nature of halogenated butyl rubber, one of the diificulties still pre-' seated at its utilization is its relatively low cure rate as compared with hi hly unsaturated rubbers such as natural rubber. Relatively fast cures are desired in various applications for rubbery copolymer-s such as extrusion of tubes, conveyor belting and wire coatings. The above described cure systems have not proven to be effective in solving this dithculty.

It has now been found that halogenated butyl rubber can be cured in a relatively short period of time to give vulcanizates of good properties, both physical and dynamic, by employing minor proportions (based on rubbery polymer) of a member of the group consisting of thiosemicarbazones, oxirne thiosemicarbazones, thiosernicarbazides and thiocarbazides. Not only is cure time reduced through the use of the above compounds as curatives, but additionally it has been found that they produce vulcan'izates of improved properties when employed for relatively long curing periods, e.g., 45 minutes.

The compositions of the present invention may be cured under a broad range of temperatures, e.g., 200 to 450 F., preferably 250 to 350 F., as well as under various conditions, e.g., open steam heating, oven curing during extrusion, molding, etc. The curing period may vary from about 2 minutes to several hours, preferably about 5 to 60 minutes, depending on temperature. Normally, about 0.1 to 20, preferably 0.5 to 10 Wt. percent based on halogenated polymer of a member of a group consisting of thiosemicarbazones, oxime thiosemicarbazones, thiosemicarbazides, and thiocarbazides is emplayed in the curing recipe.

The above compounds may be employed as the sole curing agent. Alternatively, they may be utilized in conjunction with metallic oxides such as zinc oxide, stannous oxide, magnesium oxide, etc., the metallic oxide comprising 0.5 to 25, preferably 1 to 10, Wt, percent based on halogenated polymer of the recipe. Such combinations of ingredients are particularly eifective in obtaining fast tight cures. In general, the presence of elemental sulfur as a curing agent is neither necessary nor desirable in the compositions of the present invention. Although a less desirable embodiment of the present invention, very small quantities e.-g. 0.1 to 3 wt. percent, of the present curing compounds may be used as vulcanization accelerators for conventional cure systems as opposed to being prime curing agents themselves. If desired, various members of the present group of curing agents may be used together.

Vulcanization recipes prepared in accordance with the present invention may contain various additional materials, such as carbon black, mineral fillers, pigments, antioxidants, extender oils, antitack agents, etc. If desired, blends of halogenated butyl and other rubbers, e.g., natural rubber, neoprene, butadiene-styrene polymers, etc., may be cured with the compounds of the present invention.

It is noted that although recently it has been suggested that various amine compounds may be used as curing agents for halogenated butyl rubber, the present specific class of materials is unusual in giving high quality vulcanizates within short curing periods.

Compounds suitable for the practice of the present invention may be represented by the following-generic formulas:

Thiosemic arbazones Oxime thiosemicarbazones:

NOH s (l (9 R (CH2),,-C=N-1 Thiosemicarbazides:

Thiocarbazides:

s R N l1 ll t N (1,2-dehydrothiocarbazides) Y s R, R3

R.-N=N LIL N (1,2,4,5-dehydrothiocarbazides) s R1N=Nii-N=NRz wherein n is an integer from to 10, and R R R R R and R are selected from the group consisting of hydrogen, and C to C alkyls, preferably having 1 to 10 carbon atoms, and C to C aryls.

Examples of suitable compounds are as follows:

(A) Thiosemicarbazones:

Acetaldehyde thiosemicarbazone Acetone thiosemicarbazone l-butanal thiosemicarbazone Z-butanone thiosemicarbazone Acetophenone thiosemicarbazone Benzaldehyde thiosemicarbazone Oxirne thiosemicarbazones: 2-propanone-1-al oXime thiosemicarbazone 2-propanone-1-al thiosernicarbazone oxime 2,3-pentanedione oxime thiosemicarbazone Glyoxal oxime thiosemicarbazone Benzyl oxime thiosemicarbazone Thiosernicarb azides l-phenyl thiosernicarbazide 2-benzyl thiosemicarbazide 3-methyl thi-osemicarbazide 1,3-diethyl thiosemicarbazide 1-cyclohexyl-3-methyl thiosemicarbazide T hiocarbazides 1,S diphenyl-B-thiocarbazide 1,2-dimethyl-3-thiocarbazide 1,4-ethylmethyl-3-thiocarbazide 1,2,4,5-tetramethyl-3-thiocarbazide 1,5-dimethyl-1,S-diethyl-B-thiocarbazide l-benzyl-5-ix-naphthyl-3-thiocarbazide l-phenyl-l,2-dehydro-3-thiocarbazide 1,1 di-n-buty1-4,5-dehydro-S-phenyl-3-thiocarbazide 1-benzy1-5-methyl-1,2-dehydro-3-thiocarbazide 1-a-naphthyl-4-phenethyl- 1 ,2-dehydro-3-thiocarb azide 1-cycloheXyl-5-isobutyl-1 ,Z-dehydr-o-3-thiocarbazide 1,5 -dimethyl- 1,2,4,5 -dehydro-3-thiocarbazide 1-methyl-5-phenyl-1,2,4,S-dehydro-3-thiocarbazide 5 l-allyl-S-benzyl-1,2,4,5-dehydro-3-thioearbazide l-benzyl-S-isopropyl-1,2,4,S-dehydro-B-thiocarbazide 1,5 -diphenyl-1,2,4,5 -dehydro-3-thiocarb azide 2o Chlorinated Brominated Properties Butyl Butyl Rubber A Rubber B Wt. Percent lsobutylene 98 98 Wt. Percent Isoprene 2 2 Wt. Percent Halogen.... 1. 3 2. 3 Mole Percent Unsaturation- 0.8 0. 7 Viscosity Average: Molecular Weight 375,000 400, 000

EXAMPLE 1 Chlorinated butyl rubber A was compounded with a typical thiocarb-azide, namely, 1,5-diphenyl-1,2-dehydro- 3-thiocarbazide, in accordance with the recipe shown on Table I. The various ingredients were mixed on a rubber mill in a conventional manner, their proportions being shown in parts by weight. The recipes were then vulcanized at a temperature level of 307 F. for 15 minutes and 45 minutes, respectively. The vulcanizates had the properties indicated.

Table I Compound:

Chlorinated Butyl Rubber A.- 100 100 Carbon Black 50 5O Stearic Acid.. 1. 0 1. 0 Zinc Oxide... 5.0 5.0 1,5-diphenyl-1,2-dehydro-3-thioearbazide-.. 5. 0 Cured 157307 F:

Modulus, psi/300%..- 285 2,145 Tensile, p.s.i 450 2, 280 Elongation, percent- 700 355 Cured 45 [307 F:

Modulus, psi/300% 1, 465 2,025 Tensile, p.s.i 2, 050 2, 225 Elongation, percent 410 345 Goodrich Flexorneter (45/307 F Dynamic Drift, percent..- Failed 0.0 Final Dynamic Comp., per 2. 9 Comp., Set, percent 1. 6

As shown above, vulcanizates obtained by the use of a thiocarbazide as a curing agent showed improved physical and dynamic properties when cured for both a relatively short and more extended curing times.

EXAMPLE 2 Table II Table IV 5 Compound: Compound:

Brormnated Butyl Rubber 33 100 100 100 Brominated Butyl Rubber B 100 100 100 Carbon Black (Philblaclr-O). 50 50 50 Carbon Black (Philbleok-O) 50 50 50 Steam: Acid a 1 l 1 Stearie Acid 1 l 1 Zinc Oxide 5 5 Zinc Oxide 5 5 1,2-diphen 1,2-dehydro-3-tliiocarbazide 5 3 2,3-Butanedione Oxirne Tlnosemicarha- Cured 157307" F; zone 5 3 Modulus, p.s.i./300% 1. 125 1, 475 2 545 Cured 157337" F; Teusiie, p.s.i i- 2, 350 2,640 2545 Modulus, p.s.i., 300% 1,125 1, 295 2,350 Elongation, percent 495 500 300 Elongation, Percent 495 e55 350 Cured 45'/307 F. Cured 451/307" F;

Modnlusn .i./3U0% 1,230 2.055 2.22 Modulus, p. i./3t)0% 1, 230 2, G00 2, 360 Tensile, p.s.i 2, 390 2, 535 2,390 Tensile, 13.5.1 2, 390 2,775 2,360 Elongation, percent 485 395 3 l Elongation, Percent 485 390 300 Air Oven Aging (is hours/300 F.) Cured 45'] O Goodrich Flexornctcr (45/3U7 F.):

307 F; Dynamic Drift, Percent 3.8 1 6 0. 0 Modulus, p.s.1i/3G0% .a Final Dynamic Como, Percenta 16. 3 10.1 7. 6 Tensile, p.s.i 445 950 1. 415 Comp. Set, Percent 4 1 5. 9 1. 3 Elongation, percent 240 235 225 Goodrich Flexometcr (45 I307 Ii):

ginal Dsynamic Catnip percent 16.? 10.2 crop, at per"en 6. i 2 i L l 0 Table IV illustrates that oxirne thiosernicarbazones give vulcanizates having improved properties when utilized either alone or in conjunction with zinc oxide. The imshown in Table II, vuhfanlzatfis P F provement in modulus for a minute cure is particu- P Y and y d j PIOPBYUBS are Pbtamed when thlo larly noted :as indicative of the fact that the present syscarbazides are utilized to cure brormnated butyl rubber. J tems give fast tight cures Of particular interest is the outstanding heat-aging properties thereby obtained, particularly those secured in the presence of zinc oxide. EXAMPLE 5 3O EXAMPLE 3 Chlorinated butyl rubber A was corn-pounded with throsemicarbazide, as shown in Table V. The recipes were then cured for 15 minutes, and for 4-5 minutes at 307 F., To illustrate the use of oxirne thiosemicarbazones to vulcanizates having th physical and dynamic propercure halogenated butyl rubber, chlorinated butyl rubber A r ties .indicatmi was compounded with a typical oxime thiosemicarbazone, i.e., 2,3-butanedione oxime thioseniicarbazone, in the Table V manner indicated in Table III, the proportions of materials being shown in parts by weight. The recipes were then cured at 307 F. for the periods indicated to give 40 A B vulcanizates having the properties shown in Table III.

i i t (113 t 13 oh A Ol'lnfl e 11 F U or Table 111 Carbon Black (Philblack-O)- Stearic Acid 4 Zinc Oxide Thiosernicarbazide A B Cured 157307 F.2

Modulus, nah/300%... %?nSile p.S.P Compound: ongfmm Chlorinated Butyl Rubber A 100 190 gg iig B000, Carbon Black (Philblaolr-O)-- 50 50 n v 0 Tensile, psi ilii ggg G s IF- "PITT", oodric Flexometer 307 2,3g-gi tanufllone Osirue ThiostmicarLa 3 0 Dynamic Drift, Percent u '3 Final Dynamic Como, Percent" Cured 1:) I307 F CD Set Per m UodulusJi. i. /300% 285 2,255 Ce Tensile, p.s.1 450 2, 560 r Elongation, percent 700 340 Cured 5{307 11: 3m 1 405 1L0 nus p.s.i./ u o Tensile, i).s.i 2. 050 2,3130 As indicated above, in contrast to the very low quality 3131}? iifgg gggfi gq i F vulcanizates obtained when employing a conventional D namic Drudge-recent .2 cu-re system for a short period of time, the present in g; g,f pmem vention oiifers vulcanizate having markedly improved proper-ties. Both the dynamic and physical properties of the vulcanizates obtained by the use of thiosemicarbazide were substantially better than those obtained by the use AS Illustrated 12 chlormad il g g A i ig of zinc oxide. The data illustrate that thiosemicarbazides i accordance th plesgnt ion mar e y may readily be employed in the absence of metallic improved properties, particularly with respect to a 15 oxides minute curing period.

EXAMPLE '6 EXAMPLE 4 7D In a manner similar to that previously described, Brominated butyl rubber B was compounded with an brominatcd butyl rubber B was compounded with thiooxirne thiosemicarbezone, as shown in Table IV, and the semicarbazide and cured for various periods at 307 F. various recipes then cured. The properties of the re- The vulcanizates thereby obtained had the properties suiting vnlcanizates are set forth in the following table. shown in Table VI.

Table VI Compound:

Brominated Butyl Rubber B 100 100 100 Philblack-O 50 50 50 Stearic Acid 1 1 1 Zinc Oxide. 5 5

Thiosemicarb 5 3 Cured l5/307 F.:

Modulus, p.s.i./300% 1, 125 2, 275+ 1, 680

Elongation, percent 495 280 300 Cured 457307 F.

Modulus. psi/300% 1, 230 2, 100+ 1. 800

Elongation, percent 48 30 300 Goodrich Flexometer (45/307 F.) 7

Dynamic Drift, percent 3. 8 0.0 0.0

Final Dynamic Comp, percent..- 16. 3 3t 4 11. 5

Comp. Set, percent 4. 1 1.8 1. 9

As illustrated by Table VI, vulcanizates obtained by the use of thiosemicarbazide alone or in conjunction with zinc oxide had improved both physical and dynamic properties as compared with a conventional zinc oxide cure.

Various modifications may be made to the present invention. For example, the present curing agents may be utilized with other halogenated polymers such as those derived from ethylene-propylene copolymers, ethylenebute'ne-l copoly-mers, polypropylene, chloroprene, etc.

Having described the present invention, that which is sought to be protected is set forth in the following claims.

We claim:

1. A composition comprising a halogenated rubbery copolymer containing at least 0.5 wt. percent halogen and wherein the amount of halogen and the halogen are correlated and selected from the group consisting of not more than about 1 atom of combined chlorine per double bond in the copolymer and not more than about 3 atoms of combined bromine per double bond in the copolymer and formed by copolymerizing a major portion of a C to C isoolefin with -a minor proportion of a C "to C multiolefin and halogenating the copolymer, and containing between about 0.5 and about 20.0 wt. percent based on the halogenated rubbery copolymer, of at least one nitrogen-sulfur-containing compound as a curing agent and selected from the group consisting of:

wherein n is an integer from to 10 and R R R R R and R are radicals selected from the group cons C!) W sisting of hydrogen, C to C alkyl and C to C aryl.

2. A composition as in claim 1 wherein the copolymer is a chlorinated rubbery copolymer of isobutylene and isoprene.

3. A composition as in claim 1 wherein the copolymer is a brominated rubbery copolymer of isobutylene and isoprene.

4. A composition as in claim 1 wherein the rubbery copolyme is formed with between about 85 and about 99.5 wt. percent of the isoolefin and between about 15 and about 0.5 wt. percent of the multiolefin.

5. A composition as in claim 1 wherein the nitrogen sulfur containing compound is 1,5-diphenyl-1,2-dehydro- 3-thiocarbazide.

6. A composition as in claim 1 wherein the nitrogensulfur containing compound is 2,3-butanedione oxirne thiosemicarbazone.

7. A composition as in claim 1 wherein the nitrogensulfur containing compound is thiosemicarbazide.

8. A process for vulcanizing a halogenated rubbery copolymer containing at least 0.5 wt. percent halogen and wherein the amount of halogen and the halogen are correlated and selected from the group consisting of not more than about 1 atom of combined chlorine per double bond in the copolymer and not more than about 3 atoms of combined bromine per double bond in the copolymer and formed by copolymerizing a major portion of a C to C isoolefin with a minor proportion of a C to C multiolefin and halogenating the copolymer which comprises compounding with said halogenated copolymer between about 0.5 to about 20.0 wt. percent based on the halogenated copolymer of at least one nitrogen-sulfur containing compound, as a curing agent, and selected from the group consisting of 11. A process as in claim 8 wherein the nitrogen-sul- References Cited by the Examiner fur containing compound is 1,5-diphenyl-1,2-dehydro-3- UNITED STATES PATENTS thiocarbazide.

12. A process as in claim 8 wherein the nitrogen-sul- 2'852'498 9/58 Bradley et fur containing compound is 2,3-butanedione oxime thio- 5 2'911'393 11/59 Brooks et 260 79' micarbazone 2,955,102 9/60 Clayton et a1 260-79.5

3 022 275 2/62 Lober et a1. 260-79 13. A process as in claim 8 wherein the nitrogen-sulfur containing compound is thiosemicarbazide. LEON I. BERCOVITZ, Primary Examiner. 

1. A COMPOSITION COMPRISING A HALOGENATED RUBBERY COPOLYMER CONTAINING AT LEAST 0.5 WT. PERCENT HALOGEN AND WHEREIN THE AMOUNT OF HALOGEN AND THE HALOGEN ARE CORRELATED AND SELECTED FROM THE GROUP CONSISTING OF NOT MORE THAN ABOUT 1 ATOM OF COMBINED CHLORINE PER DOUBLE BOND IN THE COPOLYMER AND NOT MORE THAN ABOUT 3 ATOMS OF COMBINED BROMINE PERDOUBLE BOND IN THE COPOLYMER AND FORMED BY COPOLYMERIZING A MAJOR PORTION OF A C4 TO C8 ISOOLEFIN WITH A MINOR PROPORTION OF A C4 TO C14 MULTIOLEFIN AND HALOGENATING THE COPOLYMER, AND CONTAINING BETWEEN ABOUT 0.5 AND ABOUT 20.0 WT. PERCENT BASED ON THE HALOGENATED RUBBERY COPOLYMER, OF AT LEAST ONE NITROGEN-SULFUR-CONTAINING COMPOUND AS A CURING AGENT AND SELECTED FROM THE GROUP CONSISTING OF: 